The mosaic, which dates from about AD380, depicts Greek hero Bellerophon riding the winged horse Pegasus and has been described as the best find of its kind in 50 years.

Anthony Beeson, an expert on classical art and a member of the Association for the Study and Preservation of Roman Mosaics, said it is ‘without question the most exciting mosaic discovery made in Britain in the last fifty years’.

Cotswold Archaeology’s chief executive Neil Holbrook said: ‘This is one of the best 4th-century classically-inspired Roman mosaics ever found in the country.